1. Field of the Invention
The present invention relates to a method and an apparatus for producing voltages, and more particularly, to a technique for producing a trimmed voltage with enhanced accuracy.
2. Description of the Related Art
These days, any electronic devices have been increasingly demanded to be reduced in size and power consumption. In particular, for example, mobile devices such as cellular phones or portable terminals are required to be reduced in size and enhanced in duration of battery operation. As a result, a demand for internal voltages being produced in the devices with enhanced accuracy has also been increased. Known as a control method for producing an accurate internal voltage is a technique of trimming a voltage by disconnecting a fuse provided internally (e.g., see Japanese Patent Laid-Open Publication No. 2000-150799)
In the aforementioned conventional technique, a fuse connected in parallel to a feedback resistor of an amplifier circuit is disconnected to provide a trimmed output voltage. In this case, a resistance component remaining within the circuit after the disconnection of the fuse would cause variations in the actual output voltage value. Moreover, since the value can be determined only after the fuse has been actually disconnected, it was difficult to improve the accuracy of trimming.